The effects of manipulating verbal suggestions on physical performance

Expectation induced by verbal suggestions is known to be a central mechanism in the generation of the placebo response in different physiological and pathological conditions. Here, we analyze the impact of different verbal suggestions in an experimental setting, measuring work performed, and rate of perceived exertion in healthy subjects undergoing strenuous exercise. A double protocol is used, with different probabilities of receiving what is believed to be an ergogenic substance (in fact, a placebo), with or without an associated conditioning procedure. We show that while high verbal suggestions of motor improvement can work alone, low verbal suggestions produce a response only after conditioning, and that in the absence of verbal suggestions (open-label placebo) no response can ever be elicited. These results can be useful for the design of both clinical trial and sports training protocols.